Semiconductor transducer

Abstract

A semiconductor transducer comprises a semiconductor strain gauge composed of a mono-crystalline semiconducting material and a strain sensing region formed in a first main surface of the mono-crystalline semiconducting material, and a strain measuring member coupled to the semiconductor strain gauge through an alloy material. An electrical insulating layer is attached to a second main surface of the mono-crystalline semiconducting material which is coupled to the strain measuring member through the alloy material. The insulating layer is extended to a side surface of the mono-crystalline semiconducting material thereby to cover the same side.

We claim: 
     
       1. A semiconductor transducer comprising: a semiconductor strain gauge composed of a monocrystalline semiconducting material portion having a first main surface, a second main surface and a side surface, and a strain sensing region formed in said first main surface of said monocrystalline semiconducting material portion;   an electrical insulating layer covering said second main surface and said side surface of said mono-crystalline semiconducting material portion;   a strain measuring member at which strain to be sensed is caused; and   an alloy material interposed between said strain measuring member and that part of said electrical insulating layer which covers said second main surface of said mono-crystalline semiconducting material portion, for coupling said strain measuring member to said second main surface through said insulating layer,   wherein said electrical insulating layer is a very thin layer having a thickness of only several μm and is made of one material selected from a group consisting of silicon dioxide, alumina, silicon nitride, germanium dioxide, gallium arsenide doped with a selected one of chromium, iron and oxygen and gallium phosphide doped with a selected one of chromium, iron and oxygen, and wherein said alloy material is one selected from a group consisting of a gold-germanium group alloy and a gold-silicon group alloy and is continuously disposed between said electrical insulating layer and said strain measuring member.   
     
     
       2. A semiconductor transducer according to claim 1, in which said insulating layer not only covers both of said second main surface and said side surface completely but extend to said first main surface to cover a part of said first main surface which is free from said strain sensing region. 
     
     
       3. A semiconductor transducer according to claim 2, in which said mono-crystalline semiconducting material portion is made of a material of one conduction type and said strain sensing region is formed by diffusion of a material of the opposite conduction type, thereby isolating said mono-crystalline semiconducting material portion from said strain sensing region by a PN junction. 
     
     
       4. A semiconductor transducer according to claim 3, in which said mono-crystalline semiconducting material portion is made of a silicon mono-crystal of P conduction type, said mono-crystalline semiconducting material portion having said first main surface formed with an N-type strain sensing region by diffusion of boron; and in which said strain measuring member is made of one material selected from a group of single substances consisting of iron, nickel, cobalt, molybdenum, tungsten and titanium and a group of alloys made of at least two materials selected from said group of single substances. 
     
     
       5. A semiconductor transducer according to claim 3, in which said mono-crystalline semiconducting material portion is made of a silicon mono-crystal of P conduction type, said mono-crystalline semiconducting material portion having said first main surface formed with an N-type strain sensing region by diffusion of boron; in which said insulating layer includes a laminated layer structure of at least two materials selected from a group consisting of silicon dioxide, alumina, silicon nitride, germanium dioxide, gallium arsenide doped with selected one of chromium, iron and oxygen, and gallium phosphide doped with selected one of chromium, iron and oxygen; and in which said strain measuring member is made of one material selected from a group of single substances consisting of iron, nickel, cobalt, molybdenum, tungsten and titanium, and a group of alloys made of at least two materials selected from said group of single substances. 
     
     
       6. A semiconductor transducer according to claim 3, in which said mono-crystalline semiconducting material portion is made of selected one of a silicon mono-crystal and germanium mono-crystal of N conduction type, said mono-crystalline semiconducting material portion having the first main surface thereof formed with a P-type strain sensing region by diffusion of gallium; and in which said strain measuring member is made of one material selected from a group of single substances consisting of iron, nickel, cobalt, molybdenum, tungsten and titanium and a group of alloys made of at least two materials selected from said group of single substances. 
     
     
       7. A semiconductor transducer according to claim 3, in which said mono-crystalline semiconducting material portion is made of selected one of a silicon mono-crystal of N conduction type, said mono-crystalline semiconducting material portion having the first main surface thereof formed with a P-type strain sensing region by diffusion of gallium; in which said insulating layer includes a laminated layer structure of at least two materials selected from a group of silicon dioxide, alumina, silicon nitride, germanium dioxide, gallium arsenide doped with selected one of chromium, iron and oxygen, and gallium phosphide doped with selected one of chromium, iron and oxygen; and in which said strain measuring member is made of one material selected from a group of single substances consisting of iron, nickel, cobalt, molybdenum, tungsten and titanium, and group of alloys made of at least two materials selected from said group of single substances. 
     
     
       8. A semiconductor transducer according to claim 3, in which said mono-crystalline semiconducting material portion is made of a selected one of a silicon mono-crystal and germanium mono-crystal of P conduction type, said mono-crystalline semiconducting material portion having the first main surface formed with a N-type strain sensing region by diffusion of phosphorus. 
     
     
       9. A semiconductor transducer according to claim 1, in which said strain measuring member is a cantilever. 
     
     
       10. A semiconductor transducer according to claim 9, in which said cantilever has flat surfaces and said semiconductor strain gauge is coupled to said cantilever at a portion of one of said flat surfaces. 
     
     
       11. A semiconductor transducer according to claim 9, in which recesses are formed at portions of surfaces of said cantilever to concentrate strain thereto when force is applied to a portion of said cantilever and said semiconductor strain gauge is coupled to said cantilever across one of said recesses. 
     
     
       12. A semiconductor transducer according to claim 1, wherein the electrical insulating layer is 1 μm or less in thickness.